This invention relates generally to techniques of lining the inner wall surfaces of hollow articles of special shapes such as oil-well pipes, bellows, and pipe bends or elbows (hereinafter referred to as "hollow article(s)"). More particularly, the invention relates to the technique of lining a hollow article which comprises inserting an inner material for lining within the hollow article and causing the inner material to expand thereby to cause it to fit tightly against the inner wall surface of the hollow article.
As is known, piping for conducting fluids such as, for example, piping in plants, oil-well piping, and piping of heat exchangers are often required to convey corrosive fluids or the like. Furthermore, hollow articles such as high-temperature, high-pressure vessels must have not only strength to withstand pressure but also corrosion resistance and leakproofness, which are important design considerations.
In piping as mentioned above, it is necessary to positively provide and maintain resistance to withstand pressure and corrosion resistance not only in the general parts of the pipe structures but also in the special pipe parts of so-called oil-well pipes, tubing, bellows, and bends and pipe parts joined to flanges, panels, etc. In such piping, these required properties can be provided by properly installed linings. In a pressure vessel, also, a positively installed inner lining is required for imparting corrosion resistance and leakproofness thereto.
In cases where the conditions of flowing and retention of corrosive fluids as mentioned above involve various temperatures, pressures, chemical constituents, and the like, there is a high probability of trouble such as stress concentration, relative displacement, buckling, and fatigue failure due to differences in coefficients of thermal expansion between the inner and outer pipes and between pipes and panels joined thereto, and between other parts. In order to keep such trouble at a minimum, it is desirable to impart as large an interference as possible between the two members thereby to obtain strong bonding and integral state therebetween.
As methods of causing an inner lining material to adhere closely to the inner surface of a hollow article, in general, techniques such as shrink fitting, and hydraulic pipe expansion have heretofore been used. In shrink fitting, however, since temperature difference is utilized, only a light gap can be obtained at the boundary between the two members, whereby this technique is disadvantageous in that it cannot be utilized for articles such as bent pipes, bellows tubes, and oil-well pipes.
In hydraulic pipe expansion, in the case where the yield stress of the hollow tube is lower than that of the inner tube, for example, the interference becomes negative. Consequently, tightening becomes impossible even when pipe expansion is carried out, whereby there are imposed restrictions relative to mutual combinations, selection, etc. of the materials.
Furthermore, both of the above two methods have a drawback in that installation of an inner lining is impossible in the case of a hollow article such as pressure vessel because such a hollow article has a special structure different from that of an article such as a pipe structure.